E-book readers...which one to choose

I've recently decided to get an ebook reader. I normally use my phone but I would like to save my battery for other thibgs as well. Having an e-reader would certainly come in handy. My problem is I don't know which one to get. Most of my files are in epub format so I would like an e-reader that can open that file type. Which do you think is the best e-reader out there. I would really appreciate the help.